diff options
author | 2022-04-25 19:57:54 +0200 | |
---|---|---|
committer | 2022-04-26 12:51:31 +0200 | |
commit | e88a6a8fece9b92be4f55735134a022061e6e68b (patch) | |
tree | ddadbbdf7e9e41c963927058f1fe1513d90c852e /drivers/android | |
parent | binder: Use kmap_local_page() in binder_alloc_copy_user_to_buffer() (diff) | |
download | linux-e88a6a8fece9b92be4f55735134a022061e6e68b.tar.gz linux-e88a6a8fece9b92be4f55735134a022061e6e68b.tar.bz2 linux-e88a6a8fece9b92be4f55735134a022061e6e68b.zip |
binder: Use memcpy_{to,from}_page() in binder_alloc_do_buffer_copy()
The use of kmap_atomic() is being deprecated in favor of kmap_local_page()
where it is feasible. Each call of kmap_atomic() in the kernel creates
a non-preemptible section and disable pagefaults. This could be a source
of unwanted latency, so kmap_local_page() should be preferred.
With kmap_local_page(), the mapping is per thread, CPU local and not
globally visible. Furthermore, the mapping can be acquired from any context
(including interrupts). binder_alloc_do_buffer_copy() is a function where
the use of kmap_local_page() in place of kmap_atomic() is correctly suited.
Use kmap_local_page() / kunmap_local() in place of kmap_atomic() /
kunmap_atomic() but, instead of open coding the mappings and call memcpy()
to and from the virtual addresses of the mapped pages, prefer the use of
the memcpy_{to,from}_page() wrappers (as suggested by Christophe
Jaillet).
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Link: https://lore.kernel.org/r/20220425175754.8180-4-fmdefrancesco@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/android')
-rw-r--r-- | drivers/android/binder_alloc.c | 13 |
1 files changed, 2 insertions, 11 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 0875c463c002..5649a0371a1f 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -1244,23 +1244,14 @@ static int binder_alloc_do_buffer_copy(struct binder_alloc *alloc, unsigned long size; struct page *page; pgoff_t pgoff; - void *tmpptr; - void *base_ptr; page = binder_alloc_get_page(alloc, buffer, buffer_offset, &pgoff); size = min_t(size_t, bytes, PAGE_SIZE - pgoff); - base_ptr = kmap_atomic(page); - tmpptr = base_ptr + pgoff; if (to_buffer) - memcpy(tmpptr, ptr, size); + memcpy_to_page(page, pgoff, ptr, size); else - memcpy(ptr, tmpptr, size); - /* - * kunmap_atomic() takes care of flushing the cache - * if this device has VIVT cache arch - */ - kunmap_atomic(base_ptr); + memcpy_from_page(ptr, page, pgoff, size); bytes -= size; pgoff = 0; ptr = ptr + size; |